linting sometimes passes in CI when it fails locally

[glyn]

Here's an example: #860

Locally:

$ SKIP_DOCKER=true make lint
golangci-lint run --config ./golangci.yml
pkg/imagestore/ocilayout/ocilayout.go:9: File is not `goimports`-ed (goimports)
	"github.com/deislabs/duffle/pkg/imagestore"
make: *** [lint] Error 1
$ echo $?
2